Windmill or Wind Turbine- powered boats: how many are out there, and are they viable?

Yes.

Rick W.

 

Yes.

and

Yes. But only with batteries. No problem going directly into the wind when you have multiply energy collection systems, a good energy storage system and good energy conversion system. The question becomes how far and how fast.

My overall efficiency from the air at the turbine to water at the prop will be:
89% 88% x 88% x 97% x 86% = 57%

It will be even lower if the batteries are called into play to average power delivery based on varying energy collection.

If you solve the problem I posed for AK in post 175 on this thread then you will get some idea of what is possible with turbine alone using the above overall efficiency. It is certainly not as good as you could get with a mechanical drive but then it is much more difficult to conveniently store the energy and drive optimisation is much more difficult.

I did consider turbine alone without solar collection but the turbine needs to be quite large to be effective in light wind. This is when hull drag is lowest so a good time to make good speed off solar or stored energy. I would have needed greater righting moment and this could only be achieved with more ballast or greater beam. Both detract from performance.

Rick W.

 

Windmaster in #162 asked a good question about why we do not yet see electric boats with multiple wind driven generators. It is a matter of size and cost. Rick wants to build a monohull, but I would suggest only a catamaran offers the greater surface area upon which to mount multiple wind driven generators.

http://www.fourwinds-ii.com/v2/?c=library&i=windGenComp

Then the batteries have to be looked at. In terms of lead acid, only Odyssey offer an improvement. Page 104 "Breakthrough"

http://www.proboat-digital.com/proboat/20080203/

I am going to leave the calculations to others, but intuitively speaking I think there is a case to be made for a length and width of catamaran than can be loaded with wind powered generators and solar panels, a suitably sized bank of Odyssey batteries to be used as a "buffer", controlled by a sophisticated inverter and powered with two electric motors. It's about economies of scale. More about the inverter and the "buffer" batteries on page 74,

http://www.proboat-digital.com/proboat/20080203/

When the Eestor ultra capacitors become available, if the costing are reliable, then Rick is going to be as happy as a dog with two tails, because the lighter Eestor units will render his monohull more viable and good luck to him.

# For a 52 kWh unit, an initial production price of $3,200, falling to $2,100 with mass production is projected. This is half the price per stored watt-hour as lead-acid batteries, and potentially cheap enough to use to store grid power at off-peak times for on-peak use.

# No degradation from charge/discharge cycles.

http://en.wikipedia.org/wiki/Eestor

http://en.wikipedia.org/wiki/Supercapacitor

Anyway, let us see what the future offers. 2009 is a year away.

Pericles

 

OK...I'm not sure about all this.

When a windmill collects wind, some of the force is turned into circular motion for generating electricity, and some of the force is trying to push the windmill against its mast.
So if you are sailing into the wind directly, the windmill is making electricity, but it is also pushing the boat backwards?

I accept the windmill must act like a spinnaker cos gyrocopters work well.

So the question is....how much energy is rotary, and how much is penalty.

Maybe Rick will need to tack his boat like a sailboat?

 

I mean if his batteries are low

 

OK I'm done now. Sorry for reducing everything down to baby-talk. Good luck with your design, Rick. I think you should do a proper test model complete with scaled down windturbine.

 

Absolutely, wind turbines fixed to the land don't have to worry about this. All they have to do is extract as much energy from the air as possible. But since a boat is not fixed to anything and is freely floating, you have to consider what effect trying to extract this energy is going to have on the boat - pushing it sideways, backwards or whatever. Thank goodness someone has taken my point about gyrocopters - at last!

 

As the boat moves forward into the wind, the apparent wind on the rotor increases and the rotor turns faster to produce more electricity to push the boat faster into the wind so the the apparent wind on the rotor increases and the rotor turns faster to produce more electricity to push the boat faster into the wind and the rotor turns faster to produce more electricity to push the boat faster into the wind so the the apparent wind on the rotor increases and the rotor turns faster to produce more electricity to push the boat faster into the wind.

Hell's teeth, so the faster you go the faster you go, which is why ice yachts go faster than wind speed. Now this only works on ice, so the sooner the oceans freeze solid, the sooner we can sail faster on the frozen oceans? Can any sailor see a downside with this? Sure we won't be able to grow crops to feed animals and ourselves and we'll be starving to death, but there has to be a silver lining somewhere behind the consequences of the Sunspot Cycle 24's failure to kick off.

http://wattsupwiththat.wordpress.com/

Bet you all wish I were joking eh?

Pericles

 

Richard
You should work through this thread. It a matter of gearing betweeen the air and the water. The effective pitch of the turbine needs to be around twice the pitch of the prop for the sytem to work going directly into the wind. The ratio of the pitches are a function of the overall efficiency. The higher the efficiency than the lower the difference in pitches.

By "effective" pitch I am including any gearing between the turbine and the prop.

It may be easier to understand if you assume efficiency of 100% and directly geared. Lets say the turbine is pitched at 2m and the prop is pitched at 1m.

Lets say apparent wind speed is 10m/s. Then perfect air turbine is doing 5rps as is the prop (direct geared). Boat will be doing 5m/s with perfect (zero slip prop). So true wind speed is 5m/s.

Power is force times velocity. Lets say the prop is generating 100N. The power will be 500W. The drag on the turbine will be 500/10 = 50N. Hence the drag on the boat is 50N.

In practice the turbine and props will have losses due to slip and induced drag. So there will be less power available to move the boat.

The nub is that you have to build a system capable of 500W to deliver 250W to the boat if you want to do the wind speed into the wind and this is with perfect turbine, perfect prop and lossless gearing. In the real world you have to account for losses so you end up transfering even more power relative to useful power. As wind speed goes up the power transfer quickly gets very large unless you alter gearing to accept boat speed to windaward slower than the windspeed.

The thing to remember is GEARING. I weigh 75kg but I can lift 10t if the gearing is suited. Just that I have to travel much further than the load travels. That is GEARING. In the case above the air turbine has air going through it twice as fast as the water passing through the prop so force will be double on the prop as the force on the turbine - GEARING.

Rick

 

If you're talking abount GEARING, why don't you talk in terms of ratio ie 2:1 or whatever? Bringing in pitch only confuses the issue!

 

The ratio of the pitches combined with any mechanical or electrical "gearing" needs to be taken into account. So pitch of both turbine and prop are important parameters in making the overall gear ratio suitable to make the boat go directly into the wind. You cannot consider the mechanical gearing in isolation of the pitch of both the turbine and prop. It is the combination that matters.

There are other factors that need to be considered beyond overall gearing but this is the important part to appreciating why it works. For example both the turbine and prop need to be sized correctly to work efficiently at their respective operating points.

So I think you are missing the point about the importance of pitch. It is integral to the overall gearing and this is the key concept I am trying to convey. I could have chosen equal pitch for turbine and prop with a 2:1 mechanical gearing to get the same result but it is important to realise that there is a turbine and prop tightly coupled through their respective pitches to different fluid media that are moving relative to each other. The slip for high aspect props, designed for high efficiency, will have slip less than 5% so it can be almost neglected - not too far from my perfect turbine/prop.

Depending on the overall gearing you can get the boat to go upwind, downwind or in "irons" with both turbine and prop stalled.

Rick W.

 

Rick
That all makes sense. I didn't realise that a windturbine is so efficient. The power it generates is high compared to the drag. That's really the main point I was looking for, and you answered that.
The gearing is just a smaller issue, to deal with all the extra losses.

I was pondering putting a windturbine on my boat....but it would need to be big for light wind, so I decided against it. Maybe just a tiny one to run the laptop and communications and my electric shaver I don't have a girlfriend so the electric shaver must follow me everywhere.


So are you still working through the problem of dismantling your hull? That would be interesting to see on your website.

 

Rick, I don't quite understand this,
Question one:
What would you say is the ideal gear ratio between the air and water elements for sailing directly to windward?
Question two:
If the wind turbine was stationary, what would be the average angle of the blades to the oncoming air? I say "average" because I guess you intend to used twisted blades. (However, for simplicity, I have always used flat untwisted blades - and very effective they have been too!) I believe that to leave the turbine blades untwisted results in "washout" at the tips (reduction in the angle of attack) and consequently a reduction in tip vortices leading to greater efficiency.
Sorry, but these are the parameters I use myself! Maybe a bit unscientific!

 

The angle of the blade sets the pitch. So your pitch varies with radius meaning the angle of attack changes with radius. This will mean the blade is not optimised but can still be quite effective. I have not looked at the performance of such a simple turbine but it is easy to do.

The effective pitch can be determined from the blade angle at 75% of radius for a first approximation. Without any calculation I guess that a suitable angle would be 65 degrees relative to the shaft or 25 degrees to the oncoming real wind angle. To some degree it will depend on the shape of the blade.

You can use 1:1 mechanical gearing providing the pitch of the prop is about one third of the turbine. With very efficient turbine and prop it is possible to operate in the right conditions with overall gearing as high as 1.6:1 but for the size of turbine I have this will only work in wind above 5m/s.

The Re# is low for small turbine in low wind and this reduces efficiency. Hence the gearing needs to be lower to get it to work. As the wind picks up the gearing can be altered to take advantage of the improving efficiency.


Rick

 

Yes, thanks, I understand it now.
As it happens, about 15 years ago. I tested such a setup as you describe here (1:1) with a 70 degree angle relative to the shaft (not much different than the 65 degrees you mention). It did work, so you are not far off in your estimations. The model boat did go very successfully against the wind. At that time I used a 3-bladed wind-turbine, if I remember rightly.